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Normal conditions Positive AO Index Ice extent in the good ol days was controlled mainly by wind variations... …but the recent thinner ice was defenseless against the attack of the AO+ during the 90s Arctic Oscillation Index Ice-age Movie From NOAAs ClimateWatch

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Ice Age is a Big Deal because… by Maslanik and Fowler, NSIDC, Arctic Report Card 2011 its a proxy for ice thickness. And THATs a big deal because a thinner ice cover is more easily melted, more easily moved by the wind, and more likely to follow a trajectory of loss as GHGs continue to increase. Thick ice

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The thinner ice cover is more mobile and more vulnerable to anomalous wind patterns, like those generated by a high-amplitude jet stream: T HE A RCTIC D IPOLE (Overland and Wang, 2010) 20072008200920102011 Thick ice of the good ol days was much less affected by these wind patterns (Wang et al, 2009)

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All that new open water absorbs additional solar radiation during spring and summer… …that heats the sea surface and adds yet more fuel to the Arctic fire… Sea surface temps SST AK

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Summary so far… GHGs = > gradual thinning GHGs = > gradual thinning Natural variability: period of AO+ flushes thick ice out of Arctic in 90s Natural variability: period of AO+ flushes thick ice out of Arctic in 90s Thinner ice cover more easily pushed by winds and melted by anomalous heat fluxes: it cant recover Thinner ice cover more easily pushed by winds and melted by anomalous heat fluxes: it cant recover Additional open water absorbs more sunlight, heats ocean surface, melts more ice Additional open water absorbs more sunlight, heats ocean surface, melts more ice Whats up with all that heat?? Whats up with all that heat?? Ice extent anomaly 1960 1970 1980 1990 2000

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During autumn and winter, energy - lots more than normal – is being transferred to the atmosphere as sensible heat, water vapor, and infrared radiation.

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Is wave amplitude really increasing? Wave amplitude measured as seasonal- mean difference in latitude between ridges and troughs at each longitude Amplitude is increasing almost everywhere Trends (OND)

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How has the spatial and temporal distribution of 500 hPa heights changed during autumn? Increased ridging north of 50 o N Decreased troughs Has wave amplitude increased or has whole pattern shifted northward?

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Where are northward elongations occurring? Ridge peaks located mainly over western N. America and eastern N. Atlantic Ridge peaks located mainly over western N. America and eastern N. Atlantic Number of ridge points north of 50 o N increasing west of Greenland Number of ridge points north of 50 o N increasing west of Greenland Autumn (OND) 300 340 260 Trends (OND)

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What about summer? from Rutgers Snow Lab Snow is melting earlier over high- latitude land Soil is exposed to sunlight earlier, so it dries and warms earlier Soil is exposed to sunlight earlier, so it dries and warms earlier Further Arctic amplification Further Arctic amplification Summersurface T anoms

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Summer (JAS) Ridge peaks and troughs shifting northward Ridge peaks and troughs shifting northward Amplitude increasing Amplitude increasing High correlations with May snow area High correlations with May snow area May snow area r = -0.9 r = -0.7